Polidoro J H, Henry A F, Taquini A C, Savino E A
Rev Esp Fisiol. 1977 Sep;33(3):221-6.
Isolated non-stripped segments of the rat tail artery, after stimulation by catecholamines or high-K, developed an isometric contraction strong enough to as, to allow easy recording of complete dose response curves. Lowering external Na to 17% of its standard concentration decreased the responses to the higher range of K concentrations whereas it enhanced those to the lower range of K concentrations. Raising external Na by 38% or decreasing it 50% did not alter responses to adrenaline. But, lowering Na enhanced those responses when arteries were rendered hypodynamic by prior immersion in a low-Ca medium. The curves depicting the relationship between Ca concentrations and tension induced by adrenaline or high-K were also studied. Curves of the arteries exposed to adrenaline were placed to the left with respect to those of K. The present data provide evidences that Na is involved in the excitation-contraction coupling processes of arterial smooth muscle. However, its role is affected when Na concentration is far below the physiological one. The effects of changing Na concentrations vary according to the K and Ca concentrations. It also reinforced the belief that adrenaline may act by increasing the Ca inward movement beyond that elicited by mere depolarization.
大鼠尾动脉的孤立非剥脱节段，在受到儿茶酚胺或高钾刺激后，会产生足够强的等长收缩，以便轻松记录完整的剂量反应曲线。将细胞外钠浓度降至其标准浓度的17%会降低对较高钾浓度范围的反应，而增强对较低钾浓度范围的反应。将细胞外钠浓度提高38%或降低50%不会改变对肾上腺素的反应。但是，当动脉通过预先浸入低钙培养基而变得收缩力减弱时，降低钠浓度会增强这些反应。还研究了描绘钙浓度与肾上腺素或高钾诱导的张力之间关系的曲线。暴露于肾上腺素的动脉的曲线相对于钾诱导的曲线向左移动。目前的数据提供了证据表明钠参与动脉平滑肌的兴奋-收缩偶联过程。然而，当钠浓度远低于生理浓度时，其作用会受到影响。改变钠浓度的影响根据钾和钙浓度而有所不同。这也强化了一种观点，即肾上腺素可能通过增加钙内流，使其超过单纯去极化所引发的钙内流来发挥作用。
